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                                  United States
                                  Environmental Protection
                                  Agency
                                  Health Effects Research
                                  Laboratory
                                  Research Triangle Park NC 27711
                                  Research and Development
                                  EPA-600/S1-81-066  Dec. 1981
Project  Summary
                                  Studies  in  Children
                                  Exposed to  Low  Levels  of Lead
                                  Herbert L. Needleman
                                    Two separate studies were con-
                                  ducted with the overall  objective of
                                  examining the impact of lead at low
                                  dose on the neuropsychological func-
                                  tion of children.
                                    In the first study, a sample of children
                                  identified as having elevated lead
                                  levels in the dentine of shed deciduous
                                  teeth (N = 19) were compared to chil-
                                  dren with low dentine lead (N = 22) on
                                  electroencephalograms and a panel of
                                  8 auditory and speech processing
                                  tasks.
                                    Quantitative electroencephalograms
                                  were obtained from 20 sites under 4
                                  conditions in these subjects. The
                                  spectrum from 0.5 - 32 Hz was  ex-
                                  amined; four bands were studied
                                  (alpha, beta, delta, and theta) under
                                  four conditions. Of the 320 compari-
                                  sons, 10 differed at P - 0.025 or less
                                  (Wilcoxin-Mann, Whitney two sample
                                  test). These 10 features, nine behav-
                                  ioral measures previously obtained,
                                  and maternal I.Q. were then submitted
                                  to multivariate analysis. A stepwise
                                  linear discriminant function analysis
                                  showed that adding the EEG to behav-
                                  ioral analysis in the model increased
                                  the  discriminating power from P =
                                  0.015 to P = 0.001.
                                    The most useful diagnostic features
                                  were EEG slowing (delta) over the
                                  parietal cortex and decreased full
                                  scale I.Q.
                                    Of the 8 speech  and auditory out-
                                  comes studied, significant differences
                                  favoring the low  lead group were
                                  found on three measures of auditory
                                  processing: (1) Goldman-Fristoe-
                                  Woodcock Auditory Selective Atten-
                                  tion Test, (2) Staggered Spondaic
                                  Word Test (Left noncompeting), (3)
                                  Speech Discrimination.
                                    This Project Summary was devel-
                                  oped by EPA's Health Effects Research
                                  Laboratory, Research Triangle Park,
                                  NC, to announce key findings of the
                                  research project that is fully docu-
                                  mented in a separate report of the
                                  same title (see Project Report ordering
                                  information at back).


                                  Introduction
                                    While the toxicity of lead at high dose
                                  is widely acknowledged, considerable
                                  controversy exists as to whether lesser
                                  doses produce adverse health effects.
                                  Lead is known to inhibit certain enzyme
                                  systems at extremely low concentra-
                                  tions. Among those most sensitive are
                                  D-aminolevulinic acid dehydrase,
                                  adenyl cyclase, and ferrochelatase. It is
                                  not, however, universally accepted that
                                  these biochemical changes and other
                                  changes represent adverse health ef-
                                  fects.
                                    For the purposes of the investigations
                                  described below, an adverse health
                                  effect is defined as "an alteration in the
                                  functioning of  an organism which di-
                                  minishes its ability to adapt to a chang-
                                  ing environment. As a result, the orga-
                                  nism's longevity, vigor, or reproductive
                                  capacity is reduced." In  a changing
                                  environment,  the ability to register
                                  change and then make decisions based
                                  upon the data  is essential to survival.
                                  The organ in which these executive

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 functions primarily reside is the central
 nervous system. The organizing princi-
 ple  of these investigations is that the
 child's CNS is a candidate site for the
 early expression  of  adverse  effects of
 lead exposure. The Lead Exposure
' Program at Children's Hospital Medical
 Center has focused on CNS performance.
 Earlier studies by the group had reported
 that children thought to be undamaged
 by lead, but who had elevated dentine
 levels, were less able on a number of
 measures of CNS  function when  com-
 pared to controls.  Among the perform-
 ances which appeared sensitive to lead
 were verbal intelligence, auditory and
 speech processing, attention and class-
 room behavior.
   This study examines the electrophysi-
 ology of the CNS of a subsample of high
 and low lead subjects, and also compares
 them on a number of other measures of
 auditory and  speech processing. A
 separate  sample  of  children from an-
 other city were evaluated by teacher
 ratings, family history, and their dentine
 lead levels measured. This offered an
 opportunity, not  only  to replicate our
 previous observations, but to evaluate
 the effects of  lead on classroom per-
 formance while controlling more  com-
 pletely for other covariates which  could
 be confounding.

 Conclusions

 Study I
   Alterations in neuropsychologicfunc-
 tion were demonstrated in electroen-
 cephalograms of asymptomatic children
 with elevated body lead burdens. These
 changes tended to be located in midline
 brain  structures. The  addition of EEC
 analysis to a  battery of psychologic
 outcomes sharpened  diagnostic pre-
 cision remarkably.
   Statistically significant decrease in
 function was found on three of nineteen
 speech processing outcomes. Outcomes
 tended to favor low  lead subjects gen-
 erally. The relatively small sample size
 may be responsible for the  failure of
 certain outcomes to reach statistical
 significance.

 Study II
   Teachers' Behavioral Ratings as a
 Function of Lead Burden.
   The proportion of  negative teachers'
1 reports of classroom behavior tended to
 increase  with  increasing dentine lead
 concentrations. The items most sensitive
 to lead were distractibility, disorganiza-
 tion, ability to follow a sequence of
directions, and overall classroom func-
tioning.
  After data reduction by cluster analy-
sis, the cluster containing the items
"distractible" and "disorganized"  was
found most sensitive to lead exposure.
The impact of lead  was evaluated by
stepwise multiple logistic regression. A
significant (p = 0.013) lead effect  was
found, controlling for major covariates.
This study replicated in part a  previous
investigation from this laboratory which
shows that teachers' assessments of
classroom behavior are sensitive to lead
exposure. It goes further than that study
by controlling for a number of covariates
that could be related  to outcome.  The
ability o'f the child to inhibit irrelevant
stimuli is critical to the task of academic
learning. The item "distractible" which
evaluates that ability is consistently
sensitive to lead exposure. It is reason-
able to expect that this deficit is related
to the impaired performance on speech
processing  measured  here.

Recommendations
  These studies add  to the weight of
those which  report  lead effects at low
dose,  and demonstrate that the threshold
for appearance of adverse behavioral
effects is a  function  of the sensitivity of
the methods brought to bear on measur-
ing outcome.
  The findings of alterations  in EEC,
speech processing,  and classroom be-
havior in samples clinically assumed to
be free of  frank toxicity  supports the
prudence and hygienic utility of reducing
lead  in the environment available to
children.
  Studies of lead effects in  children,
should attend to those behaviors which
are expressions o'f the organism'sability
to focus attention.

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   Herbert L. Needleman, formerly with Children's Hospital Medical Center, Boston,
     MA, is now with the University of Pittsburgh School of Medicine, Western
     Psychiatric Institute and Clinic, Pittsburgh, PA 15261.
   Carl Hayes is the EPA Project Officer (see below).
   The complete report,  entitled "Studies in  Children Exposed to Low Levels of
     Lead," (Order No.  PB 82-108 432; Cost: $8.00,  subject to  change)  will be
     available only from:
           National Technical Information Service
           5285 Port Royal Road
           Springfield, VA  22161
           Telephone: 703-487-4650
   The EPA  Project Officer can be contacted at:
           Health Effects Research Laboratory
           U. S.  Environmental Protection Agency
           Research Triangle Park, NC 27711
ff U S GOVERNMENT PRINTING OFFICE, 1981 — 599-017/7409

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